Skin-Friendly Hook Fastening Component

ABSTRACT

A skin-friendly hook component of a hook and loop fastener that reduces or eliminates the occurrence of red-marking and/or irritation if brought into contact with a wearer&#39;s skin. In one embodiment, the hook component can have a relatively large top surface area among the hooks with respect to a surface area of the hook backing. In another embodiment, the hook backing is highly flexible, attributable to a flexible resin and/or modified topography. In yet another embodiment, a highly flexible polymer, or polymers, can be used to make individual hooks such that the hooks bend in response to a minimum amount of pressure. Various illustrated hook tapes have features along their edges to enhance skin-friendliness. A skin-friendly hook component results any combination of the disclosed embodiments. The hook component is particularly beneficial when used in absorbent articles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority under 35 U.S.C.§ 121 to U.S. application Ser. No. 09/793,057, filed on Feb. 26, 2001,the entire contents of which are hereby fully incorporated by reference.

TECHNICAL FIELD

This invention is directed to a hook component of a hook and loopfastener. More particularly, the hook component reduces skin irritationtypically caused by most hook components.

BACKGROUND

A number of fastening systems, such as diaper fastening systems,incorporate a hook and loop system for easy fastening and release. Thehook component typically includes a flat plastic sheet laminate with anumber of protruding hooks that engage with a number of loops on a loopcomponent. The protruding hooks and rigid, flat, plastic backing of thehook component can produce red-marking and irritation if brought intocontact with a person's skin, such as an infant's skin in contact with ahook component of a diaper fastening system.

Improvements to hook and loop fasteners often dwell on performance, suchas improved engagement or maximized peel and shear strength. However,such improvements do not eliminate the problem of skin irritation.

There is a need or desire for a hook component of a hook and loopfastener that reduces or eliminates the occurrence of red-marking and/orirritation if brought into contact with a person's skin.

SUMMARY

The present invention is directed to a skin-friendly hook component of ahook and loop fastener. In one embodiment of the invention, thecollection of hooks can have a large aspect ratio. In another embodimentof the invention, the hook component can have a highly flexible hookbacking. In yet another embodiment of the invention, the hook componentcan be made of a highly flexible polymer. Any of these improvements tothe hook component, or a combination of these improvements, result in askin-friendly hook component that is soft to the touch and reduces oreliminates the occurrence of red-marking and/or irritation if broughtinto contact with a person's skin.

More particularly, hook components having a large percentage of hookaspect ratio, in relation to surface area of the hook component backing,reduce the threat of skin irritation compared to hook components havinga small percentage of hook aspect ratio coverage. Hook aspect ratiomaximization can be achieved through a combination of individual hookshaving large aspect ratios and a relatively high density of hooks on thehook component.

Flexible hook backing material is also beneficial in terms ofskin-friendliness. Flexible material can bend in response to pressure,thereby not poking a wearer with hooks the way rigid hook backings do.One method of making the hook backing more flexible is by reducing itsthickness. The topography of the hook backing material can also beoptimized to create regions of varying thicknesses or apertures thatcontribute to a highly flexible hook backing. The hook backing may alsobe made from a flexible polymer.

A hook component made of a highly flexible polymer can flex and bendcorrespondingly with a wearer's movements, both at a large flat-tapescale, and also at a small micro-hook level. Due to the flexibility,edges of the hook component are less likely to poke the wearer. Also,each individual hook bends in response to pressure, thereby alleviatingstresses that could lead to skin irritation.

A hook component made of a highly flexible polymer, and/or with a highlyflexible backing, and/or having a collection of hooks with a largeaspect ratio significantly reduces skin irritation due to the greatlyreduced stress responses to pressure.

With the foregoing in mind, it is a feature and advantage of theinvention to provide a hook component of a hook and loop fastener thatreduces or eliminates the occurrence of red-marking and/or irritation ifbrought into contact with a person's skin.

This hook component is particularly suitable for use in fasteningsystems on disposable absorbent articles. Examples of such suitablearticles include diapers, training pants, feminine hygiene products,incontinence products, other personal care or health care garments,including medical garments, or the like.

The invention features an improved hook component for use with a matingloop component for hook and loop fastening, the hook component includinga hook backing and a plurality of hooks protruding from one side of thehook backing.

According to one aspect of the invention, the hook component has anoverall aspect ratio, as defined herein, within a range of 40 to 55percent (preferably, 45 to 50 percent; more preferably, about 47percent).

For some applications, the hooks comprise a polymer selected from thegroup consisting of elastomeric thermoplastic polymers and metallocenecatalyzed polymers.

The hooks are arranged on the hook backing, in some embodiments, in adensity of 155 to 310 hooks per square centimeter (preferably, 186 to279 hooks per square centimeter; more preferably, 202 to 248 hooks persquare centimeter).

In some cases, the hooks are J-shaped and/or have heads of molded resinand/or have at least one flat lateral side.

According to another aspect of the invention, the hook backing has anon-uniform thickness with areas of greater thickness about the hooksand areas of lesser thickness between the hooks.

Preferably, the hook component has tapered edges about a periphery ofthe hook backing.

Preferably, at least a portion of the hook backing has a thickness in arange from a positive amount to 3.5 mils (88.9 microns), more preferablyfrom 0.5 mil (12.7 microns) to 3.0 mils (76.2 microns), and mostpreferably from 1.0 mil (25.4 microns) to 2.5 mils (63.5 microns).

The hook backing may be provided with a knurled texture on at least onesurface, or apertures therethrough, for improved flexibility.

According to another aspect, a plurality of the hooks each have at leastone rounded free end, and each of the hooks comprises a polymer having abulk flexural modulus in a range of 7 kpsi (48 MPa) to 30 kpsi (207Mpa), preferably 7 kpsi (48 MPa) to 25 kpsi (173 Mpa), and morepreferably 7 kpsi (48 MPa) to 15 kpsi (104 MPa).

In some embodiments, the hook backing comprises a polymer having a bulkflexural modulus in a range of 7 kpsi (48 MPa) to 90 kpsi (621 Mpa),preferably 7 kpsi (48 MPa) to 70 kpsi (483 Mpa), and more preferably 7kpsi (48 MPa) to 50 kpsi (345 MPa).

According to another aspect of the invention, the hook componentusefully includes more than one feature of the invention for improvedskin-friendliness. In one such combination, the hook component has anoverall aspect ratio within a range of 20 to 55 percent, the hookbacking has a non-uniform thickness with areas of greater thicknessabout the hooks and areas of lesser thickness between the hooks, andeach of the hooks comprises a polymer having a bulk flexural modulus ina range of 7 kpsi (48 MPa) to 30 kpsi (207 Mpa).

According to another aspect, the hook component includes at least onerow of edge transition members protruding from the backing between onelongitudinal edge of the backing and the array of hooks, the edgetransition members being of a height less than the nominal height of thehooks. Preferably, at least two rows of edge transition members protrudefrom the backing between the longitudinal edge and the array of hooks,with the edge transition members of an outer row being of a lesserheight than the edge transition members of an inner row disposed betweenthe hooks and the outer row of edge transition members. More preferably,three rows of edge transition members protrude from the backing betweenthe longitudinal edge and the array of hooks, with the edge transitionmembers of each row being taller than the members of any transitionmembers closer to the longitudinal edge.

In some embodiments, the edge transition members are of molded form,and/or have upper surfaces angled away from the nearby longitudinaledge.

According to another aspect, the hook component includes at least onerow of end transition members protruding from the backing between oneend of the backing and the array of hooks, with the edge transitionmembers being of a height less than the nominal height of the hooks.Preferably, at least two rows of end transition members (e.g., threerows) protrude from the backing between the end of the backing and thearray of hooks, with the end transition members of an outer row being ofa lesser height than the end transition members of an inner row disposedbetween the hooks and the outer row of end transition members.

According to yet another aspect, the hook component has an edge skirtprotruding from the side of the backing between a longitudinal edge ofthe backing and the array of hooks. The skirt extends of a heightgreater than the nominal height of the hooks and is disposedsufficiently close to the array of hooks that when deflected toward thearray of hooks the skirt extends over an upper edge of a closest row ofhooks. Preferably, the edge skirt is integrally molded with the backing.

According to another aspect, the backing of the hook component is moldedto form a V-shaped protrusion extending out of the plane of the backingtoward the side of the backing from which the hooks protrude, with theV-shaped protrusion disposed between the array of hooks and an edge ofthe backing.

In another aspect of the invention, a laminate has a bottom layerlaminated to a hook component for use with a mating loop component forhook and loop fastening. The hook component includes a generally planarhook backing and a plurality of hooks arranged in an array andprotruding from a side of the hook backing opposite the bottom layer.Notably, as laminated, the backing of the hook component forms adiscrete, V-shaped protrusion extending out of the plane of the backingaway from the bottom layer, with the V-shaped protrusion disposedbetween the array of hooks and an edge of the backing.

In some preferred embodiments, the bottom layer extends beyond onelongitudinal edge of the hook component for attaching the laminate to agarment (e.g., a diaper or another of the types of garments discussedabove) to serve as a garment closure

In some cases, the backing of the hook component is molded to form theV-shaped protrusion.

The invention also provides a method of forming a laminate hookcomponent, the method including securing a hook tape to an underlyinglayer of material. The hook tape has a generally planar hook backing anda plurality of hooks arranged in an array and protruding from a side ofthe hook backing opposite the underlying layer of material, and the hooktape secured to the underlying layer of material in such a manner thatthe backing of the hook component forms a continuous protrusionextending out of the plane of the backing toward the side of the backingfrom which the hooks protrude, between portions of the backing securedto the underlying layer of material. The protrusion is disposed betweenthe array of hooks and an edge of the backing.

In some applications the method includes, prior to securing the hooktape to the underlying layer of material, creasing the hook tape alongspaced-apart hinge points to cause a portion of the backing to bend outof its plane for forming the protrusion.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a hook component and a loop component prior toengagement with one another;

FIG. 2 is a front view of an individual hook of a hook component havinga rounded free end;

FIG. 3 is a side view of an individual hook of a hook component havingat least one rounded free end;

FIG. 4 is a side view of an individual hook of a hook component havingat least one rounded free end;

FIG. 5 is a side view of an individual hook of a hook component havingat least one rounded free end;

FIG. 6 is a front view of an individual hook of a hook component havingtwo rounded free ends;

FIG. 7 is a front view of an individual hook of a hook component havinga flat free end;

FIG. 8 is a side view of an individual hook of a hook component having aflat free end;

FIG. 9 is a perspective view of a hook component;

FIG. 10 illustrates the determination of the hook head size forcalculating aspect ratio;

FIG. 10A shows the hook head area as the area of the upper face of theparallelepiped shown in dashed outline in FIG. 10; and

FIG. 11 is a perspective view of a hook component having a hook backingof varying thickness.

FIG. 12 is a top view of a hook tape with the hooks of neighboringlongitudinal rows aligned in the transverse direction.

FIG. 12A is a top view of a hook tape with the hooks of neighboringlongitudinal rows staggered in the transverse direction.

FIG. 13 is an end view illustrating skin contact with an edge hook rowof a prior art hook tape.

FIG. 14 is an end view illustrating skin contact with an edge of animproved hook tape with edge transition features.

FIG. 15 is an end view of an improved hook tape having a second form oftransitional edge features.

FIG. 16 is a side view illustrating skin contact with a hook and the endof a prior art hook tape.

FIG. 17 is a side view illustrating skin contact with a hook and the endof an improved hook tape with end transitional features.

FIG. 18 also shows end transitional features near a hook member.

FIG. 19 is a perspective view of an improved hook tape section havingboth end and edge transition features.

FIG. 20 is an end view of a hook tape having an edge skirt.

FIG. 20A is an end view illustrating skin contact with the longitudinaledge of the hook tape of FIG. 20.

FIG. 21 is a perspective view of the hook tape of FIG. 20.

FIG. 22 is a cross-section of a portion of a mold roll configured toform the hook tape of FIG. 21.

FIG. 23 is a longitudinal cross-section through a diaper tab having asection of improved hook tape secured across the tab, the hook tapeincluding a continuous edge guard.

FIG. 24 is a cross-sectional view through a molding cavity for formingthe wide hook of FIG. 5.

Like reference symbols in the various drawings indicate like elements.

DEFINITIONS

Within the context of this specification, each term or phrase below willinclude the following meaning or meanings.

“Aspect ratio” refers to the relative hook head density of a hookcomponent. This ratio is related to the area of the engaging head of ahook that corresponds with the maximum instantaneous displaced area of amating loop component as the hook head penetrates the loop component. Inthe context of the invention, it affects the feel of the hook componentas the hook heads come into contact with a person's skin. The aspectratio is measured as the aggregate hook head area divided by the overallarea of the hook component. The hook head area is measured at anelevation above the hook backing that includes the maximum overhang ofthe hook head.

“Cross-machine direction” refers to a direction parallel with the hookbacking and perpendicular to the lateral direction of maximum overhangof a hook. Mushroom-shaped hooks with equal overhang on all sides haveno defined cross-machine direction.

“Flexible” refers to materials which are compliant and which willreadily conform to the general shape and contours of the objects incontact with the materials.

“Machine direction” refers to a direction parallel with the hook backingin the lateral direction of maximum overhang of a hook, as opposed to“cross-machine direction” which refers to a direction generallyperpendicular to the machine direction. Mushroom-shaped hooks with equaloverhang on all sides have no defined machine direction.

“Medical garment” includes medical (e.g., protective and/or surgical)gowns, caps, gloves, drapes, face masks, blood pressure cuffs, bandagesand the like.

“Non-pointed” refers to a surface that is blunt or smooth, and does nottaper to a single point.

“Polymers” include, but are not limited to, homopolymers, copolymers,such as for example, block, graft, random and alternating copolymers,terpolymers, etc. and blends and modifications thereof. Furthermore,unless otherwise specifically limited, the term “polymer” shall includeall possible geometrical configurations of the material. Theseconfigurations include, but are not limited to isotactic, syndiotacticand atactic symmetries.

“Releasably attached,” “releasably engaged” and variations thereof referto two elements being connected or connectable such that the elementstend to remain connected absent a separation force applied to one orboth of the elements, and the elements being capable of separationwithout substantial permanent deformation or rupture. The requiredseparation force is typically beyond that encountered while wearing theabsorbent garment.

“Thermoplastic” describes a material that softens when exposed to heatand which substantially returns to a nonsoftened condition when cooledto room temperature.

“Topography” refers to the surface features of an object, includingheight and texture.

These terms may be defined with additional language in the remainingportions of the specification.

DETAILED DESCRIPTION

As shown in FIG. 1, a hook component 20 and a loop component 22 can bebrought together to be releasably attached, or releasably engaged, toone another. The hook component 20 has a number of individual hooks 24protruding generally perpendicularly from a resilient hook backingmaterial 26. Similarly, the loop component 22 has a number of individualloops 28 protruding generally perpendicularly from a resilient loopbacking material 30. The individual hooks 24 and the individual loops28, when brought into contact with one another, engage with one another,with the hooks 24 latching onto the loops 28, until forcibly separated,thereby pulling the hooks 24 out of the loops 28.

The individual loops 28 of the loop component 22 can be needled,stitched or otherwise projected through the loop backing material 30,which can suitably be made from a non-woven material. The individualloops 28 can suitably be made from a fibrous non-woven web such as aspunbond non-woven web, or a staple fiber carded web. Alternatively, theindividual loops 28 can be made of yarn or tow. Once the loops 28 havebeen formed, fibers forming the loops can be anchored in place bybonding the fibers to the loop backing material 30 with heat and/oradhesives or any other suitable means. Such suitable loop components 22are available from Velcro USA, of Manchester, N.H.

The hook component 20 can include any of a number of improvements, orcombinations thereof, to render the hook component 20 skin-friendly.Virtually any hook shape can be used. For example, the individual hooks24 can have non-pointed free ends 32 to prevent poking of a wearer'sskin. Individual hooks 24 having a simple, rounded free end 32 are knownin the art. FIG. 2 shows an individual J-shaped hook 24 with a free end32 rounded in the machine direction. The machine direction is indicatedby an arrow 34 in FIGS. 1, 2, 6, 7, 10 and 11. Consequently, the term“cross-machine direction” refers to a direction normal to the machinedirection. The cross-machine direction is indicated by an arrow 36 inFIGS. 3-5, 8 and 10.

The free end 32 of the hook 24 shown in FIG. 2 is rounded in the machinedirection and can be, but does not necessarily have to be, rounded inthe cross-machine direction as well. FIG. 3 shows the hook 24 of FIG. 2in the cross-machine direction, wherein the free end 32 of the hook 24is not rounded in the cross-machine direction. FIG. 4 shows the free end32 of the hook 24 of FIG. 2 as rounded in the cross-machine direction. Awide, rounded free end 32 renders the hook 24 more skin-friendly thancurrent hooks having narrower widths, due to a greater area in contactwith a wearer's skin. Individual hooks 24 having a large aspect ratio inan uppermost region of the hook 24, opposite the hook backing material26, tend to be gentle on a wearer's skin because these large aspectratios, particularly with rounded edges, do not poke the wearer the waypointed ends do. FIG. 5 shows the free end 32 of the hook 24 of FIG. 2also rounded in the cross-machine direction and having a relativelylarge width, which can be molded in a cavity 102 spanning multipleadjacent mold rings, as shown in FIG. 24. The widths vary depending onover-all sizes of the hooks 24 and the loops 28.

As shown in FIG. 6, the hook 24 can have more than one non-pointed freeend 32. In this embodiment, the hook 24 has two rounded free ends 32opposite one another. These two free ends 32 are rounded in the machinedirection, as shown in FIG. 6, and can be non-rounded or rounded in thecross-machine direction, as shown in FIGS. 3-5.

The term “non-pointed” free end 32 includes hooks 24 having a roundedfree end, and also includes hooks 24 having a relatively flat free end32, suitably with a rounded edge 42 about a top surface 44 of the flatfree end. A mushroom-shaped hook 24 having a flat free end 32 is shownin FIG. 7. The hook 24 in this embodiment can look the same in themachine direction (FIG. 7) as in the cross-machine direction (FIG. 8),in which case a base portion 38 of the hook 24 is suitably round orsquare as viewed from above. Alternatively, the base portion 38 of thehook 24 can be oblong, rectangular, triangular, or any other suitableshape.

Referring to FIGS. 2-8, non-pointed free ends 32 on the hook component20 reduce skin irritation by reducing any stress responses by the wearerdue to a larger area in contact with a wearer's skin in comparison to apointed free end. The embodiments shown in FIGS. 5-8 each have aparticularly large aspect ratio in contact with a wearer's skin and arethus more skin-friendly than hooks 24 having a small aspect ratio.Individual hooks 24 having a large aspect ratio, such as non-pointedfree ends 32, can be located across an entire surface of the hookcomponent 20, or at least along an outer edge or edges 40 of the hookcomponent 20 where the individual hook texture is most apparent to thewearer, as shown in FIG. 9.

FIGS. 10 and 10A illustrate how the hook head area is determined forcalculating the aspect ratio of the hook component. The head area iscalculated at an elevation “E” corresponding to the maximum lateraloverhang of the hook head at 50, as the area of the upper face 46 of thesmallest parallelepiped (shown in dashed outline) having its base at “E”and parallel to backing 26, its front face intersecting maximum overhangpoint 50, and completely containing the portion of the hook head aboveelevation “E”. As shown in FIG. 10A, the hook head area is the productof perpendicular dimensions “W” and “L”. An individual hook 24 having alarge head area in contact with a wearer's skin is more skin-friendlythan an individual hook 24 having a small head area, such as a pointedend, in contact with a wearer's skin. Additionally, a hook component 20having a high hook density, i.e., number of hooks per square centimeter,other factors being equal, is generally more skin friendly than a hookcomponent 20 having a low hook density, also due to the greater aspectratio. Thus, skin-friendliness can be achieved through individual hooks24 having a large amount of area in contact with a wearer's skin, or ahook component 20 having a high hook density, or suitably, a hookcomponent 20 having a high density of individual hooks 24 with each hook24 having a large head area. Preferably, the aspect ratio of hookcomponent 20 is in a range of 40 percent to 55 percent. More suitably,the aspect ratio of hook component 20 is in a range of 45 to 50 percent,and most preferably, about 47 percent.

Preferably, the point 50 of maximum overhang occurs at an elevation “E”that is very close to the most upper surface of the hook. Thus, it ispreferable to minimize the penetration distance 48 for optimumskin-friendliness.

Skin-friendly hook components having an aspect ratio of greater than 40percent can be achieved, as mentioned, through individual hooks 24 eachhaving a large head area, particularly when in combination with asufficiently large hook density. A hook density of 1000 to 2000 hooksper square inch (155 to 310 hooks per square centimeter) providesoptimum spacing for a skin-friendly and useful hook component 20 formany garment applications. A hook density of 1200 to 1800 hooks persquare inch (186 to 279 hooks per square centimeter) is even morepreferred, and a hook density of 1300 to 1600 hooks per square inch (202to 248 hooks per square centimeter) is most desirable. As indicated,high hook density results in a large aspect ratio, providing the feel ofa nearly smooth texture. For example, hooks 24 having a relatively flatfree end 32, as shown in FIG. 7, are particularly suitable for providinga smooth texture when closely spaced to one another on a hook component20. The improved feel is understood to be at least in part becausepressure exerted on a wearer's skin by the hook component 20 is moreevenly distributed across a large area compared to a less densearrangement of hooks 24.

The hooks 24 are spatially arranged in rows on the hook backing 26.Flexibility of the hook backing 26 can be improved by changing thetopography of the hook backing by varying the texture and/or thicknessof the backing 26 along the surface of the backing 26. For example, theareas where the hooks 24 extend from the backing 26 can be thicker thanareas between the hooks 24, thereby enabling the areas between the hooks24 to bend with ease in response to force, or simply conform to awearer's body. The thickness can be adjusted on either a top surface 52of the hook backing 26, as shown in FIG. 11, or a bottom surface 54 ofthe hook backing 26, or on both the top and bottom surfaces 52, 54 ofthe hook backing 26. The thickness of backing 26 can also be adjusted bychanging the texture of the backing 26 on either the top surface 52, thebottom surface 54 or both surfaces 52, 54. The texture can be patternedor somewhat random, and can be produced by using, for example, apatterned or knurled roll against which the backing 26 is pressed whilein a pliable stage during the manufacturing process. In an alternativeembodiment of the invention, hook backing 26 can be foraminous, withapertures 56 formed in the hook backing between individual hooks 24, asshown in FIG. 9. The apertures 56 lower the overall resistance of thebacking to flexing and bending out of its plane.

The hook backing 26 suitably has a thickness ranging from a positiveamount to 3.5 mils (88.9 microns), suitably 0.5 mil (12.7 microns) to3.0 mils (76.2 microns), more suitably 1.0 mil (25.4 microns) to 2.5mils (63.5 microns), with thickness varying across the surfaces 52, 54.More specifically, areas between the hooks 24 can have a thicknessranging from 0 mils (0 microns), i.e. apertures, to 3.0 mils (76.2microns), suitably 0 mils (0 microns) to 2.5 mils (63.5 microns), moresuitably 0 mils (0 microns) to 2.0 mils (50.8 microns), while the areasunderneath and adjacent hooks 24 can have a thickness ranging from apositive amount to 3.5 mils (88.9 microns), suitably 0.5 mil (12.7microns) to 3.0 mils (76.2 microns), more suitably 1.0 mil (25.4microns) to 2.5 mils (63.5 microns). Furthermore, the edges 40 of hookbacking 26 about a periphery of the hook component 20 may be suitablytapered to provide minimal resistance against a wearer's skin. The hookbacking material 26 contributes toward skin-friendliness with itsconsiderable flexibility and soft surface. More particularly, theconsiderable flexibility reduces stiffness along the edges 40 of thehook component 20, thereby further enhancing skin-friendliness.

The hooks 24 and the hook backing 26 are generally produced from thesame material in one process. One suitable method of manufacture is thecontinuous molding method described by Fischer in U.S. Pat. No.4,794,028, the contents of which are hereby incorporated by reference asif set forth in their entirety. In the Fischer process, the hook backing26 and hooks 24 are simultaneously formed of a single continuous flow ofmolten resin, with the backing 26 formed under pressure in a nipadjacent a rotating mold roll having blind cavities in which the hooks24 are molded, cooled and then released by stripping the cooled backingfrom the mold roll after leaving the nip. The mold roll is typicallymade of many circular mold plates each having hook-shaped notches cutthrough at their perimeters for molding a continuous row of hooks. Themold plates are alternated with solid spacer plates that form the flatlateral sides of the hook cavities. The hook 24 of FIG. 10 isillustrative of the flat-sided hooks molded in such cavities. In somecases, the hook cavities do not extend completely through the moldplates, such that only one side of each hook is flat. In other cases,mold rings having aligned concave hook cavity surfaces are placedtogether such that the resulting hook cavities have curved lateralsides, for forming hooks as shown in FIGS. 4 and 5, for example.

Although the tooling required to mold flat-sided hooks is generallyconsidered to be simpler and less expensive to form than tooling forcurve-sided hooks, sharp edges at the intersection of the flat hooksides and the upper surface of such hooks have been found to detractfrom a desirably soft feel against skin. Thus, the improvementsdescribed herein are of particular advantage as applied to such hooks,and to molded hooks in general.

The process known in the art as “cut and stretch”, in which a softenedpolymer is extruded through a die having an elongated base opening (forextruding backing 26) contiguous with multiple hook-profiled openings(for extruding longitudinal rails having desired hook profiles), is alsosuitable for forming hook components of some hook shapes. Afterextrusion, the extruded rails are slit transverse to the extrusiondirection, and the extruded backing stretched in the extrusion directionto separate the slit rail segments to form rows of individual hooks. Thebacking may also be stretched in the direction perpendicular to theextrusion direction, to reduce the backing thickness and increase thelateral distance between neighboring hook rows.

The hooks 24 of the hook component 20 may be made of a highly flexiblepolymer, or polymers, thereby enabling the hooks 24 to flex and bendcorrespondingly with a wearer's movements. When made of a highlyflexible polymer, free ends 32 of the hooks 24 are less likely to poke awearer's skin, thereby irritating the skin, in comparison to hooks madeof less flexible polymers. Hooks 24 made of a flexible polymer bend inresponse to pressure, thereby alleviating stresses that could lead toskin-reddening or other types of skin irritation. If made of a flexiblepolymer, hooks 24 bend under a minimum amount of vertical pressure.Suitably, the polymer or polymers used to make the hooks 24 have a bulkflexural modulus in a range of 7 kpsi (48 MPa) to 30 kpsi (207 MPa).More suitably, the polymer or polymers used to make the hooks 24 have abulk flexural modulus in a range of 7 kpsi (48 MPa) to 25 kpsi (173MPa). Most suitably, the polymer or polymers used to make the hooks 24have a bulk flexural modulus in a range of 7 kpsi (48 MPa) to 15 kpsi(104 MPa).

Suitable flexible polymers for the hooks 24 include elastomericthermoplastic polymers made from block copolymers such as polyurethanes,copolyether esters, polyamide polyether block copolymers, polyesterblock amide copolymers, ethylene vinyl acetates (EVA), block copolymershaving the general formula A-B-A′ or A-B likecopoly(styrene/ethylene-butylene),styrene-poly(ethylene-propylene)-styrene,styrene-poly(ethylene-butylene)-styrene,(polystyrene/poly(ethylene-butylene)/polystyrene,poly(styrene/ethylene-butylene/styrene) and the like.

Commercial examples of suitable elastomeric copolymers are those knownas KRATON® materials which are available from Shell Chemical Company ofHouston, Tex. KRATON® block copolymers are available in severaldifferent formulations, a number of which are identified in U.S. Pat.Nos. 4,663,220, 4,323,534, 4,834,738, 5,093,422 and 5,304,599, herebyincorporated by reference.

Other useful elastomeric materials include polypropylene, polyethylene,and polyurethane elastomeric materials. Examples of such polyurethaneelastomeric materials include those available under the trademarksESTANE® from B. F. Goodrich & Co. and MORTHANE® from Morton ThiokolCorp., polyester elastomeric materials such as those available under thetrade designation HYTREL® from E.I. du Pont de Nemours & Company ofWilmington, Del., and those known as ARNITEL®, formerly available fromAkzo Plastics of Arnhem, Holland and now available from DSM of Sittard,Holland.

Commercially available examples of thermoplastic elastomers based onpolypropylene include SARLINK®, available from DSM Engineering Plastics,Evansville, Indiana; SANTOPRENE®, available from Advanced ElastomerSystems, Akron, Ohio; and UNIPRENE®, available from Teknor Apex,Pawtucket, R.I. ESCORENE® PD-3445, available from Exxon Chemical Co.,Houston, Tex., is another flexible polypropylene but is not elastomeric.

Metallocene catalyzed polymers are another type of material suitable forhooks 24. A relatively new class of polymers, metallocene catalyzedpolymers have excellent elasticity, and a narrow polydispersity number,e.g., Mw/Mn is 4 or less and may be produced according to themetallocene process. The metallocene process generally uses a catalystthat is activated, e.g., ionized, by a co-catalyst.

Metallocene process catalysts include bis(n-butylcyclopentadienyl)titanium dichloride, bis(n-butylcyclopentadienyl)zirconium dichloride,bis(cyclopentadienyl)scandium chloride, bis(indenyl)zirconiumdichloride, bis(methylcyclopentadienyl)titanium dichloride,bis(methylcyclopentadienyl)zirconium dichloride, cobaltocene,cyclopentadienyltitanium trichloride, ferrocene, hafnocene dichloride,isopropyl(cyclopentadienyl,-1-fluorenyl)zirconium dichloride,molybdocene dichloride, nickelocene, niobocene dichloride, ruthenocene,titanocene dichloride, zirconocene chloride hydride, zirconocenedichloride, among others. A more exhaustive list of such compounds isincluded in U.S. Pat. No. 5,374,696 to Rosen et al. and assigned to theDow Chemical Company. Such compounds are also discussed in U.S. Pat. No.5,064,802 to Stevens et al., also assigned to Dow.

The hook backing 26 may be made from the same flexible polymers listedabove as suitable for the individual hooks 24. A co-extrusion or layeredextrusion process can be employed to form the individual hooks and thebacking from different polymers in the same process.

Hooks 24 may be formed in a wide range of sizes. Preferably, the hookshave an overall height in a range of about 0.033 to 0.51 centimeter, anda maximum lateral head dimension of about 0.025 to 0.033 centimeter.

A skin-friendly hook component 20 results from many combinations of thedisclosed features. For example, an advantageous hook component 20 canhave a relatively large aspect ratio, and/or a flexible hook backing 26,and/or can be made of a flexible polymer. The improved flexibility ofboth the hook backing material 26 and the individual hooks 24contributes to a soft, smooth texture of the hook component 20.Furthermore, a flexible hook backing 26 enables hooks 24 made of aflexible polymer to bend in response to minimum pressure, therebyreducing the threat of irritation to a wearer, yet provides enough roombetween the hooks 24 to enable the hooks 24 and the loops 28 to engageone another.

We have also realized that subjective personal impressions of theroughness of the feel of hook tape is affected by the extent to whichthe skin and its underlying tissue conforms about a particular feature.The more the structure and arrangement of the surface features allow theskin to conform about them, the greater the perception that the surfaceis “rough” or “abrasive”, or that the subject has been “poked” by thefeature in question.

FIGS. 12 and 12A illustrate how the arrangement of hooking members in agiven array can affect the feel of the hook tape. In the tape 60 of FIG.12, J-shaped hooking members 62 (each shown as a rectangle with an arrowfacing toward the tip of the hooking member) are aligned in transverserows with open base areas between the rows. One open base area 64 isshown in dashed outline for illustration. Because this open space 64 isunrestricted in the transverse direction, contacting skin penetratesdeeper into the array of hooking members than in the array of hookingmembers on the hook tape 66 of FIG. 12A. The longitudinal distance“d_(L)” between adjacent hooking members 60 in each row is 0.030 inch inboth FIG. 12 and FIG. 12A. Reducing “d_(L)” will also reduce skinconformance, but can also reduce hook performance. In the improved hooktape of FIG. 12A, conformance is also restricted in the transversedirection by hooking members 60 of adjacent, staggered rows. Whileactual skin penetration will be at least a combined second orderfunction of the longitudinal and transverse dimensions of any open spacebetween hooking members, the area of the largest internal open space isone approximate indication of the perceived roughness of the hook array.For reasonable feel quality, the maximum bounded open area or courtyard68 within an array of hooking members is preferred to be less than about0.010 square inch (more preferably, less than about 0.005 square inch,and even more preferably, less than about 0.001 square inch).

FIG. 13 shows how the edge row of hooks 62 in a traditional hook tape 60results in rather poor skin conformance at the edge of the hook tape. Afinger 70 is shown moving across the hook tape from its edge,significantly indented by the exposed upper edge of the outer row ofhooks 62.

To reduce this effect and thereby improve the feel of the hook tape, thehook tape 72 of FIG. 14 is provided with three rows of edge transitionelements 74 of staggered height, with an outer row of quite shortelements 74, a second row of slightly larger elements, and so forth,such that the contacting skin surface 70 is gently guided up to thefunctional hooking members 62 without significant indentation. While theedge transition elements 74 of FIG. 14 are shown as having flat,horizontal upper surfaces, other element shapes can be employed tofurther reduce roughness. For example, the tape of FIG. 15 has elements74′ with tapered upper surfaces 76 that are inclined toward the adjacentedge of the hook tape. These and other shapes of transitional elementscan be provided on the hook tape at very little cost, molded along withthe hooking elements in the Fischer process by incorporating moldingrings with appropriately configured cavities, arranged between adjacentspacer plates as are the hooking element molding rings. Such molded edgetransition elements 74 may be hump-shaped, for example. Alternatively,standard hook tape with full-height hooking elements along the edge canbe modified after molding to transform the outer few edge rows ofhooking elements along each side into height-staggered transitionalelements, such as by passing the hook tape edge under a heated, taperedroller.

The ends of a cut section of hook tape can be provided with similartransition elements, as end transition elements along the end edge ofthe cut section. FIG. 16 shows how, particularly with J-hook or palmtree hooking members with exposed tips facing the end of the section oftape, contacting skin 70 can be “poked” by the edge row of hookingmembers. As shown in FIGS. 17 and 18, our improved hook tape is equippedwith three rows of molded, hump-shaped end transition elements 78 ateither end, helping to ease the transition of the contacting skin uponto the array of functional hooking members 62. Molding such endtransition elements 78 in a traditional Fischer molding process in whichthe hooking members face in the machine directions requires modifiedhooking member mold rings with end transition element cavitiespositioned at predetermined positions about their periphery.Furthermore, the transverse cutting of such a molded tape into sectionsfor use, for example, on diaper tabs, must be controlled to sever thehook tape at the proper location with respect to the molded endtransition elements. A preferred alternative is to transform thefunctional hooking members 62 adjacent a transverse cut as the tape iscut into sections. For example, the cutting mechanism can be equippedwith heated, tapered flanges for permanently deforming the adjacenthooking elements.

Both edge and end transition elements can be used to advantage on asingle section of hook tape, as illustrated in FIG. 19. In thisembodiment, tape 80 has two end rows 82A and 82B of end transitionelements 78, and three edge rows 84A, 84B and 84C of edge transitionelements 74. It is noted that a single structure may function both as anend transition element and an edge transition element.

FIGS. 20 and 21 shows another means for improving the edge comfort ofmolded hook tape. Hook tape 86 is equipped with a longitudinallycontinuous, integrally molded skirt 88 extending from base 90 betweenthe longitudinal edge of the base and the array of hooking members 62.As a skin surface 70 moves into the hook array from the edge of the tape(FIG. 20A), skirt 88 is deflected to drape over the edge row of hookingmembers and reduce perceived roughness. During normal engagement with amating surface (e.g., a loop member), skirt 80 is thin enough to buckleor be otherwise readily displaced so as to not significantly interferewith the fastening.

Skirt 88 can be integrally molded, for example, in a channel 90 definedwithin a skirt-molding ring 92 of a Fischer-type mold roll, as shown inFIG. 22. Preferably, such a channel 90 is slightly tapered for easystripping of the molded hook tape.

The molded hook tape 94 of FIG. 23 has a base 96 that, along itslongitudinal edge, is molded to have a continuous rib 98 extendingalongside the array of hooking members 62. Rib 98 may be molded as adiscontinuity in the otherwise planar base 96, such as by molding thebase in a nip (not shown) between a molding roll defining a V-shapedrib-forming channel, and a pressure roll with a V-shaped protrusionextending into the channel. With a section of the molded hook tape 94secured to a diaper tab 100 as shown, rib 98 forms a flexible cushion tohelp to transition the skin 70 onto the array of hooking members. Theopen ends of the cushion can later be closed down against the diapertab, such as with a hot, tapered iron that can be employed tosimultaneously form end transition members of molded end hooking membersof the tape, as discussed above.

As an alternative to molding the hook tape base 90 to have a V-shapeddiscontinuity 98, as shown, the tape base may be molded with threespaced, longitudinal grooves (not shown) to serve as living hinges toenable the hook tape to be pleated as it is secured to the diaper tab toform rib 98.

It will be appreciated that details of the foregoing embodiments, givenfor purposes of illustration, are not to be construed as limiting thescope of this invention. Although only a few exemplary embodiments havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention, which isdefined in the following claims and all equivalents thereto. Further, itis recognized that many embodiments may be conceived that do not achieveall of the advantages of some embodiments, particularly of the preferredembodiments, yet the absence of a particular advantage shall not beconstrued to necessarily mean that such an embodiment is outside thescope of the present invention.

1. A hook component for use with a mating loop component for hook andloop fastening, the hook component including a hook backing and aplurality of hooks protruding from one side of the hook backing; whereinthe hook backing has a non-uniform thickness with areas of greaterthickness about the hooks and areas of lesser thickness between thehooks.
 2. The hook component of claim 1, further comprising taperededges of the hook backing about a periphery of the hook component. 3.The hook component of claim 1, wherein at least a portion of the hookbacking has a thickness in a range from a positive amount to 3.5 mils(88.9 microns).
 4. The hook component of claim 1, wherein at least aportion of the hook backing has a thickness in a range from 0.5 mil(12.7 microns) to 3.0 mils (76.2 microns).
 5. The hook component ofclaim 1, wherein at least a portion of the hook backing has a thicknessin a range from 1.0 mil (25.4 microns) to 2.5 mils (63.5 microns). 6.The hook component of claim 1, wherein the hook backing has a knurledtexture on at least one surface of the hook backing.
 7. The hookcomponent of claim 1, wherein the hook backing comprises a foraminoushook backing defining apertures through the backing between adjacenthooks.
 8. The hook component of claim 1, wherein the hooks comprise apolymer selected from the group consisting of elastomeric thermoplasticpolymers and metallocene catalyzed polymers.
 9. An absorbent articlecomprising the hook component of claim
 1. 10. A diaper comprising thehook component of claim
 1. 11. A training pant comprising the hookcomponent of claim
 1. 12. A feminine hygiene product comprising the hookcomponent of claim
 1. 13. An incontinence product comprising the hookcomponent of claim
 1. 14. A medical garment comprising the hookcomponent of claim 1.